The Bloomberg School of Public Health at Johns Hopkins University put out this press release on a paper by Rudolph, Stuart, Vernick, and Webster:
…A 1995 Connecticut law requiring a permit or license – contingent on passing a background check – in order to purchase a handgun was associated with a 40 percent reduction in the state’s firearm-related homicide rate, new research suggests.
gun licensing, gun registration, Problems with Public Health Research